Real-time implementation of MRAS rotor time constant estimation for induction motor vector control based on a new adaptation signal

Abstract

Purpose The major disadvantage of the field-oriented control (FOC) scheme of induction motors is its dependency on motor parameter variations because of the temperature rise. Among the motor parameters, rotor resistance is a parameter that can degrade the robustness of FOC scheme. An inaccurate setting of the rotor resistance in the slip frequency may result in undesirable cross coupling and performance degradation. To overcome this disadvantage, the purpose of this paper is to propose a model reference adaptive system (MRAS) rotor time constant tuning to improve the induction motor drive performance and to compensate the flux orientation error in vector control law. Design/methodology/approach First, the dynamic model and the indirect field-oriented control of induction motor are derived. Then, an inverse rotor time constant tuning is proposed based on MRAS theory where a new adaptation signal formulation is used as reference model, and the estimated stator currents obtained from induction motors (IM) state space resolution is used in the adaptive model. Findings The effectiveness and robustness of IM speed control with the proposed MRAS inverse rotor time constant estimator is verified through MATrix LABoratory/Simulink model simulation and laboratory experimental results. The simulation and experimental results show good transient drive performances, satisfactory for rotor resistance estimation and robustness with regard to uncertainties and load torque disturbance. Originality/value This paper presents an online tuning of the inverse rotor time constant using a new adaptation signal MRAS model. The proposed estimator is proved to guarantee the stability for different operating conditions, especially in very low/zero speed region and heavy load torque. The stability analysis of the proposed estimation procedure is also demonstrated.

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“…In the IM, temperature changes depending on the induced heat due to the power losses and skin effect respect to the rotor frequency lead to changes in the stator resistance (R s ) and the rotor resistance (R r ) [23,24]. If the exact value of R s and R r are not known, the motor flux is estimated incorrectly by the EKF, and in this case deteriorated control performance is obtained from the IM drive system [25,26]. Furthermore, in the EKFs where the IM speed is estimated as a state using the IM dynamic model, the load torque (t L ) changes directly affect the estimation performance.…”